The invention relates generally to optical devices such as polymer-based waveguides. More particularly, the invention relates to optical devices exhibiting reduced shrinkage during manufacture, and thus improved light transmission characteristics and device reliability.
Modern high-speed communications systems are increasingly using optical waveguides including fibers for transmitting and receiving high-bandwidth data. The excellent properties of optical waveguides with respect to flexibility and ease of handling and installation are an important driving force for their implementation in high bandwidth, short-haul data transmission applications such as fiber to the home, local area networks, high-speed computing, and automotive information, diagnostic, and entertainment systems, to mention only a few.
In any type of optical communication system there is the need for interconnecting different discrete components. These components may include active devices, such as lasers, detectors, fibers modulators, and switches, for example, and passive devices such as filters and splitters, for example. Polymer-based waveguides offer a viable and potentially inexpensive way of interconnecting these components. Such waveguides should be able to couple light into or out of other optical fibers and components with good efficiency, and deliver optical signals with very low propagation losses. Such losses, in turn are determined primarily by the quality of the polymer, the waveguide structure, and the device boundary.
A proper selection of polymeric materials is necessary for making polymeric optical waveguides that display low attenuation and improved environmental stability without an excessive increase in scattering loss. Moreover, a well-defined introduction of light-confining or light-scattering elements is potentially useful to obtain controlled propagation of light in polymeric optical waveguides.
Waveguide structures can be formed by several techniques. For example, ridge waveguides can be formed by coating a lower clad and core layer onto a substrate, patterning the core by etching or development to form a ridge, and over-coating with an upper clad layer. As another example, embedded or channel waveguides can be formed by coating a lower clad and core material over a substrate, defining the waveguide by UV exposure and depositing an upper clad layer over the formed waveguide. Reactant diffusion occurs between the unexposed core and surrounding clad layers into the exposed core area changing the refractive index (hereinafter also referred to as “RI”) of the exposed region to form the waveguide.
During the formation of conventional waveguide structures, severe shrinkage can occur. This can result in movement of the original waveguide away from the end of the optical fiber that formed the waveguide, thus increasing the scatter loss of light traveling through the bulk material due to poor coupling between the fiber tip and the formed waveguide. Techniques proposed to reduce shrinkage problem in the device may require complicated optimization and costly design processes. In certain types of structures and particular applications, the shrinkage problem becomes particularly severe. For example, single-mode optical transmission fibers are often extremely small (much smaller than fibers used for multi-modal transmission). Even relatively modest shrinkage can lead to severe mismatches in alignment of light transmitting pathways between the linked fibers, resulting in unacceptable loss of coupling and consequently poor efficiency.
It would therefore be desirable to have a new waveguide structure to reduce these losses. There is also a need for improved polymer formulation and processing that help reduce the shrinkage of the polymer material structures during processing, thereby facilitating fabrication of reduced loss waveguides. A general need also exists for improved material formulation that can be used for other optical structures, such as planar waveguides, lenses, gratings, and the like.